Precision Cosmological Constraints on Atomic Dark Matter

TL;DR

This paper investigates atomic dark matter's effects on cosmological observables, exploring its parameter space and showing it can address the H0 and S8 tensions better than standard models.

Contribution

It provides the first comprehensive analysis of atomic dark matter's parameter space and its potential to resolve key cosmological tensions.

Findings

Atomic dark matter can better fit H0 and S8 measurements than ΛCDM.

Preferred parameters include specific ranges of dark photon coupling and temperature ratio.

Dark proton mass remains unconstrained by current cosmological data.

Abstract

Atomic dark matter is a simple but highly theoretically motivated possibility for an interacting dark sector that could constitute some or all of dark matter. We perform a comprehensive study of precision cosmological observables on minimal atomic dark matter, exploring for the first time the full parameter space of dark QED coupling and dark electron and proton masses $(\alpha_{D}, m_{e_{D}}, m_{p_{D}})$ as well as the two cosmological parameters of aDM mass fraction $f_{D}$ and temperature ratio $\xi$ at time of SM recombination. We also show how aDM can accommodate the $(H_0, S_8)$ tension from late-time measurements, leading to a better fit than $\Lambda$CDM or $\Lambda$CDM + dark radiation. Furthermore, including late-time measurements leads to closed contours of preferred $\xi$ and dark hydrogen binding energy. The dark proton mass is seemingly unconstrained. Our results serve as an important new jumping-off point for future precision studies of atomic dark matter at non-linear and smaller scales.